1. Field of the Invention
The present invention relates generally to a rear wheel suspension of a bicycle. In particular, the present invention relates to an electronically controlled suspension apparatus which absorbs forces caused by terrain without dissipating a rider's pedaling energy.
2. Description of the Prior Art
The pastime of bicycle riding has grown enormously over the last several years with the advent of a new species of bicycle commonly referred to as a Mountain Bike or an All-Terrain Bike ("ATB"). Because of its sturdy construction, rigid frame, wide tires, and stable ride, casual riders are often seen pedaling ATBs on city and suburban streets. One of the primary advantages and attractions of ATBs, however, is its ability to be operated off-road on rustic trails. Because of the ATB's rigid frame and wide tires, riders can be heard screaming down mountain paths and seen jumping and riding over rocks, streams, and fallen trees.
Whether riding on surface streets or mountain trails, ATB riders seek the most comfortable possible ride from their bicycle. In general, ATBs with rigid frames rely on wide tires and a small amount of natural flexibility in the frame and front forks to absorb the bumps and dips encountered on roads and trails. Often, the natural flexibility and tires provide sufficient shock absorption for riding over irregular pavement. The severe terrain of off-road riding, however, requires something more than frame flexing to smooth the ride.
In an effort to lessen the wear and tear on an ATB rider, wheel suspension systems have developed to dampen the transmission of terrain-induced shocks and vibrations to the rider. Typically, these suspension systems use a spring to support the sprung mass (i.e., the rider and bicycle frame above the spring) and a damper to control the rate of suspension movement. Many of these wheel suspension systems use an air-oil system for their suspension. In such systems, the oil is used as the damper and the air is used as the spring.
Although a bicycle having a rear wheel suspension system has a smoother ride as compared to simple frame dampening, it has created other problems for the rider. For example, unlike on most other types of vehicles where only the road surface causes the suspension to compress, on a bicycle two forces cause the rear wheel suspension to compress: the road surface or terrain and the rider's body (or mass) movement during pedaling. As a result, the suspension absorbs the forces imparted by the terrain but it also dissipates the pedaling forces imparted by the rider. Thus, in situations when a rider exerts maximum effort, such as during accelerations or hill climbs, the rear wheel suspension detracts from the rider's performance because the suspension reacts to the force of the rider's efforts and absorbs energy desirably directed into driving the rear wheel.